Secondary Erythrocytosis Due To a Cerebellar Hemangioblastoma: Demonstration of Erythropoietin mRNA in the Tumor

RYTHROPOIETIN (Ep) is a glycoprotein hormone E produced mainly by the kidney and is the principle regulator of erythropoiesis.' The level of Ep is normally tightly controlled and helps to maintain a relatively constant red blood cell (RBC) mass.' Occasionally, abnormal production of Ep results in secondary erythrocytosis. Secondary erythrocytosis has been reported in a variety of tumors including cerebellar hemangioblastoma, a rare intracranial neoplasm.' First recognized in 1943 by Carpenter et al,' secondary erythrocytosis in cerebellar hemangioblastoma has been reported to occur in up to 20% of patient^.^,' Erythropoiesis-stimulating activity has been found within tumor cyst fluid,6-8 tumor extract^,'^'^ cerebrospinal and, occasionally, ~erum.'"~'~ However, direct evidence that these tumors were actively synthesizing Ep was lacking. The recent cloning of the human Ep gene'4sL5 has provided molecular probes for the definitive identification of Epproducing tissues. We report the presence of Ep in the tumor cyst fluid and the detection of Ep mRNA in the tumor from an erythrocytotic patient with a cerebellar hemangioblastoma. This finding confirms the tumor as the site of the ectopic Ep production.